The invention relates to a valve apparatus for controlling flow through a conduit, such as municipal water supply conduits of any size, the valve being positionable to attain any Position between open and closed positions thereof.
Large fluid control valves, as used in municipal water supplies, have been known for many years and to the inventor's knowledge are of two main general types. The first type has a moveable valve member which is complementary to a valve seat and can be positioned at any position between fully opened and fully closed, and requires a heavy duty actuator to move the valve member against fluid forces, at least in one direction. A valve of this type can use a screw-threaded actuator, which can be either manually-actuated directly, or it can be actuated from a remote location if necessary through a power source. With large diameter water conduits, the force involved in moving the valve member can be considerable, requiring heavy duty actuators.
The second type of valve utilizes fluid pressure to assist in moving the valve member between open and closed positions. A valve of this type is disclosed in U.S. Pat. No. 4,295,631 (Allen) which discloses a main valve controlled by a solenoid actuated servo valve having a fixed axially extending servo valve outlet tube extending through a central opening in a diaphragm valve member. An open end of the tube is fixed and serves as a servo valve seat. The main valve is closed by a spring and fluid pressure on one side of the diaphragm is referenced with the outlet pressure and is used to assist in opening the valve against the spring. A short stroke solenoid provides simple, low power operation of the valve between either fully opened or fully closed positions, and the reference does not disclose means to position the diaphragm in any intermediate Position.
U.S. Pat. No. 4, 553,732 (Brundage et al) discloses a servo operated flow regulating valve which can be remotely controlled by varying energization of a solenoid. The valve has a normally-closed, spring-biased, pressure differential-actuated main valve element, and a pressure-compensated, servo flow valve using a solenoid. The solenoid controls a variable flow of fluid through the servo valve which controls pressure difference across the main valve element. This valve requires a spring to apply a closing force in one direction, which is overcome by fluid forces in an opposite direction, and would be appropriate for hydraulic flow valves of relatively high pressures (e.g. up to 6,000 pounds square inch) and presumably of relatively small diameter when compared with municipal water valves.
U.S. Pat. No. 4,477,051 (Ben-Yehuda) discloses a flow control valve having a closure element responsive to differential pressure between pressure in a valve cavity and main fluid Pressure on an opposite side of a diaphragm separating the cavity from the main fluid. A fixed metering orifice controls Pressure in the cavity and the valve may be closed manually by turning a threaded handle. This method of closure contrasts with the two earlier patents discussed above, both of which disclose a spring-closed valve member. Use of a main valve spring to position the valve member in either closed or open positions requires use of a high force actuator to overcome force from the valve spring, which can present problems when operating valves remotely. None of the devices disclosed in above patents would be appropriate for large valves that are used for controlling large fluid flows such as found in municipal water supplies.
To the inventor's knowledge, there are no valves which use pressure differential across the valve to apply power for shifting the valve to attain intermediate positions between the open and closed positions.